Adjustable dumbbell base



FIG. 1 is an isometric view of the adjustable dumbbell base in accordance with the present invention;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a left side elevation view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is an isometric view of the adjustable dumbbell base, wherein the broken line showing of the adjustable dumbbell is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for an adjustable dumbbell base, as shown and described. 